"Gravity wave" busts stormy forecast

By looking at regional rainfall from Thursday, you notice the Baton Rouge area is conspicuously dry when compared with areas west and east. Didn’t the WBRZ Weather Team forecast rain for much of the area? Yes. Then what happened?

Overall, the atmosphere was stable—which is why the given chance for severe storms was low. However, an advancing cold front forced air upward and sparked showers, thunderstorms, and likely, what is known as a “gravity wave.”

The National Weather Service defines a gravity wave as, “a wave created by the action of gravity on density variations in the stratified atmosphere. A generic classification for lee waves, mountains waves, and many other waves that form in the atmosphere.”

The air in our atmosphere, just like water in the ocean, is fluid and behaves as such. Imagine a wave over the open water. It builds, reaches an apex and falls. In the atmosphere, air can do the same but only on a day where there are stable layers in the atmosphere. When there is instability abound, gravity is overcome and vertical motions can persist, uninterrupted.

Thursday Morning, a nasty line of showers and thunderstorms erupted as air was lifted through a stable layer in the atmosphere. A tornado was even spawned near Lake Charles. However, gravity then caused stable air to sink east of that line, nixing out rain and storms in the Baton Rouge area. Again, the wave began building to the east and the rising motions set off more showers and storms near the Mississippi border.

Extremely difficult to detect, even with advanced satellite technology, the waves had an affect on the forecast that was easy to see. While a batch of rain was still expected in the Thursday Morning broadcast, by noon on Thursday, less than 10% of the WBRZ Weather forecast area had picked up precipitation.